This invention relates to the technology of stabilizing the operation of semiconductor integrated circuit devices, and in particular to a technology that can effectively be used to highly accurately detect the level of the supply voltage of a flash memory.
Semiconductor integrated circuit devices such as flash memories are generally provided with a so-called supply voltage detector for detecting the voltage being supplied from the power source to drive the semiconductor integrated circuit device and for outputting a detection signal representing the detected voltage.
Thus, the semiconductor integrated circuit device starts accepting external input signals applied to it when the supply voltage detector detects that the supply voltage exceeds a certain level after the device is energized or after a fall of the supply voltage. When the supply voltage is lower than that level, the internal circuits of the semiconductor integrated circuit device are reset.
The supply voltage detector comprises a so-called reference voltage generator that includes a resistor and a MOS (metal oxide semiconductors) transistor; and an inverter which is adapted to receive the generated reference voltage input to the input section of the inverter and to detect the level of the supply voltage on the basis of the reference voltage.
For a more detailed description of semiconductor integrated circuits of the type under consideration, reference should be made, inter alia, to xe2x80x9cDenshi-Zairyo (Electronics and Materials)xe2x80x9d, PP. 32-37, No. 6, Vol. 34, ed. Masashi Oshima, Kogyo-chosakai (Industrial Research Institute), Jun. 1, 1995.
However, the inventors of the present invention have found that the known supply voltage detector arranged in a semiconductor integrated circuit has a drawback as described below.
Namely, the level of the supply voltage as detected by the supply voltage detector can fluctuate depending on the potential of driving the MOS transistor that varies as a function of temperature, the electric current flowing through the resistor, the fluctuations of the logical threshold value of the inverter, the threshold value of the MOS transistor that varies as a function of the manufacturing process, the fluctuations of the resistance of the resistor and/or other factors.
The fluctuations of the detection level have become no longer negligible as a result of the use of a low supply voltage in recent years for semiconductor integrated circuit devices. What is worse, in some cases, such fluctuations can lead to operation errors on the part of the semiconductor integrated circuit device.
Therefore, an object of the present invention is to provide a semiconductor integrated circuit device whose reliability is remarkably improved by minimizing the fluctuations of the detection level of the supply voltage due to the manufacturing process and/or other factors.
According to the invention, the above objects are achieved by providing a semiconductor integrated circuit device having a supply voltage detecting means, said supply voltage detecting means comprising:
a first reference voltage generating section which, based on an operation control signal, outputs a base-emitter voltage as a reference voltage;
a detection voltage generating section which generates a detection voltage from a supply voltage of the integrated circuit device; and
a signal amplifying section which, based on the operation control signal, amplifies a differential voltage between the reference voltage generated by said first reference voltage generating means and the detection voltage generated by said detection voltage generating means and which outputs a detection signal representing said differential voltage.
In another aspect of the invention, there is also provided a semiconductor integrated circuit device having a supply voltage detection means, said supply voltage detecting means comprising:
a second reference voltage generating section which, based on an operation control signal, generates a reference voltage with a band-gap type reference voltage source using a bipolar transistor;
a detection voltage generating section which generates a detection voltage from a supply voltage of the integrated circuit device; and
a signal amplifying section which, based on the operation control signal, amplifies a differential voltage between the reference voltage generated by said second reference voltage generating means and the detection voltage generated by said detection voltage generating means and which outputs a detection signal representing said differential voltage.
Preferably, in a semiconductor integrated circuit device according to the present invention, said detection voltage generating section includes first and second resistors connected in series between the supply voltage and the reference voltage so as to generate said detection voltage by dividing said supply voltage.
Preferably, in a semiconductor integrated circuit device according to the present invention, said detection voltage generating section includes an operation control section for operationally controlling the detection voltage generating section based on the operation control signal.
With any of the above described arrangement, some of the major advantages of the present invention will be listed below.
(1) According to an aspect of the present invention, the signal amplifying section amplifies the differential voltage representing the difference between the reference voltage generated by the first reference voltage generating section and the detection voltage generated by the detection voltage generating section, and outputs it as detection signal so that the fluctuations of the supply voltage level can be minimized and highly stabilized.
(2) According to another aspect of the present invention, the signal amplifying section amplifies the differential voltage representing the difference between the reference voltage generated by the second reference voltage generating section by using a band gap type reference voltage source and the detection voltage generated by the detection voltage generating section, and outputs it as detection signal so that the fluctuations of the supply voltage level can be minimized and highly stabilized.
(3) Additionally, according to the present invention, the operation of a semiconductor integrated circuit device can be stabilized to improve the reliability thereof on the basis of (1) and (2) above.
The other objects and the novel features of the present invention will become apparent from the following detailed description made by referring to the accompanying drawings.